The United Nations' main nuclear watchdog believes that North Korea has up to six nuclear weapons, its chief said yesterday.

Asked by CNN whether it was its assessment that the North Koreans already had as many as six nuclear bombs, the head of the International Atomic Energy Agency, Mohamed ElBaradei, said: "I think that would be close to our estimation.

"We knew they had the plutonium that could be converted into five or six weapons. We know that they have the delivery system."

According to US intelligence reports, Pyongyang is believed to have two or more crude nuclear bombs.

North Korea declared in February that it had developed nuclear weapons to defend itself from the United States.